Recently, various brands and new types of mobile phones have been pushed one by one. What I want to talk to you today is about the full fit technology of the screen.From the perspective of the structure of the mobile phone screen, it can be roughly divided into three parts: protective glass, touch screen and display screen from top to bottom. These three parts need to be fitted. According to the fitting method, they can be divided into full fitting and frame fitting.Frame paste is also called mouth adhesive bonding, that is, simply fix the four sides of the touch screen and the display screen with double-sided adhesive; There is an air layer between the display screen and the touch screen.Full bonding technology is to completely paste the display screen and touch screen with water glue or optical glue.Advantages of full bonding processThe screen can isolate dust and moisture. The air layer of ordinary bonding mode is easy to be polluted by environmental dust and water vapor, which affects the use of the machine; The full bonding OCA glue fills the gap, the display panel is closely bonded with the touch screen, and there is nowhere for dust and water vapor to enter, maintaining the cleanliness of the screen.Better display effect. The full fit technology eliminates the air between the screens, and can greatly reduce the reflection of light and the loss of transmitted light, so as to improve the brightness and enhance the display effect of the screen.Reduce noise interference. The close combination of touch screen and display panel can not only improve the strength, but also fully fit, which can effectively reduce the interference of noise on touch signal and improve the smoothness of touch operation.Make the fuselage thinner. The full fit screen has a thinner body. The touch screen and the display screen are bonded with optical glue, with an increase of only 25 m50 M thickness; It is 0.1mm-0.7mm thinner than the ordinary fitting method.Disadvantages of full bonding processThe process is complex, the production yield is low, the rework is difficult, the equipment investment cost is high, and the requirements for the workshop environment are higher.Full fit technology directionIn cell technologyIt refers to the technology of embedding the functions of the touch panel into the LCD pixels, that is, the touch sensor function is embedded in the display screen. Therefore, the original three-layer protective glass touch screen display screen has become two-layer protective glass display screen with touch function, which can make the screen lighter and thinner. This technology is mainly developed by panel manufacturers, and the threshold is relatively high.In cell technology screen layers: the in cell screen consists of a surface glass bonded LCD layer (the touch screen is on the LCD layer), with a total of 2 layers.On cell technologyOn cell refers to the method of embedding the touch screen between the color filter substrate and the polarizer of the display screen, that is, the touch sensor is equipped on the liquid crystal panel, which is much less difficult than the n-cell technology.On cell is mostly used in Samsung AMOLED panel products, but it has not been able to overcome the color inequality caused by thinness and touch.On cell technology screen layers: touch screen and LCD layer bonded by surface glass, 3 layers in total.OGS / tol TechnologyOGS technology is to integrate the touch screen with the protective glass, coat the conductive layer on the inner side of the protective glass, and directly conduct coating and lithography on the protective glass. Because a piece of glass and one-time bonding are saved, the touch screen can be made thinner and lower cost.TOL refers to the small chip manufacturing process of OGS, that is, the frame BM and functional electrode are made after the white glass is tempered. The strength of its products is higher than that of OGS in large-scale process, but the cost is also high due to low process efficiency. Many domestic mobile phone brands have adopted OGS technology. However, OGS still faces the problems of strength and processing cost, which need to increase the strength through secondary strengthening.OGS technology screen layers: LCD layer bonded by OGS layer, 2 layers in total.Other traditional full paste technologiesGG, PG, GF, g1f, GF2, GFF, etc. need to be bonded twice. The thickness is relatively thick and the yield is not high.Screen permeability: OGS is the best, in cell and on cell are the second, and GFF is the worst.Lightness: in cell is the lightest and thinnest, which is one of the reasons why mobile phones such as I phone and P7 can be made thinner. OGS and on cell are the second, and GFF is the worst.Screen strength: GFF > on cell > OGS > in cell.Touch effect: strictly speaking, the touch sensitivity of OGS is better than that of on cell / in cell, but touch is also related to the underlying optimization of mobile phone system. For example, the touch experience of I phone with in cell is much better than that of many Android phones.Cost and technical difficulty: in cell / on cell is more difficult and the cost is higher, followed by OGS / tol. GFF has the lowest cost and technical difficulty, so it is mostly used on thousand yuan machines.Lamination process classificationAt present, full bonding is mainly divided into two processes:·Loca (water glue) bondingOCA fitOCA (optically clear adhesive) is a special adhesive used to bond transparent optical elements (such as lenses). It is required to be colorless and transparent, the light transmittance is more than 90%, the bonding strength is good, it can be cured at room or medium temperature, and it has the characteristics of small curing shrinkage.It is mainly applicable to the fitting of small-size products, and each product needs mold opening, which is expensive and the fitting cost is high; There are no special requirements for the material of the bonding product, and the thickness is generally 100um, 125um, 150um, 175um, 200um, etc.advantage:High production efficiency, uniform thickness, no glue overflow problem, controllable bonding area, no corrosion problem and no yellowing.technological processThe full lamination process of OCA is more complex than that of water glue, because it needs the intervention of die-cutting factory.At present, many large full lamination plants (including TP plant and module plant) do not have their own corresponding die-cutting stations, so the first supplier of full lamination OCA is large and medium-sized die-cutting plants, so there are many problems in cooperation.The die-cutting factory will take the die-cutting performance of OCA and the appearance of products as the main acceptance criteria and test basis.The full lamination factory mainly takes the filling (i.e. bubble discharge), rework and reliability of OCA as the main acceptance criteria and test basis.To sum up, the process flow of OCA is actually divided into two parts:·Die cutting process flow of OCA·Die cutting process flow of full lamination OCALamination process flow of full lamination OCATraditional OCA full bonding process (OGS / GFF / GG /...)Loca bonding, liquid optical clear adhesive, English Name: liquid optical clear adhesive, is a special adhesive mainly used for bonding transparent optical elements.Colorless and transparent, light transmittance of more than 98%, good bonding strength, and can be cured under normal or medium temperature conditions. At the same time, it has the characteristics of small curing shrinkage and yellowing resistance.It is mainly suitable for large-size lamination, curved surface or complex structure lamination, high ink thickness or uneven surface lamination.Advantages: it can adhere curved surface or uneven surface materials, is not sensitive to ink thickness, is easy to rework, and the cost is lower than that of OCA.Loca operation mode:The loca shall be defoaming after sub packaging and before use, and the sub packager with reasonable design shall be selected. After transportation, it can be used after standing for 24 hours before initial use.Loca full bonding process flowFull fit key equipmentCommon defects of full fit:Paraticle (foreign body)FiberDirtyBubbleMisalignmentFunctio test failForeign matters and debrisWe need to distinguish the sources and treat them differently. If the appearance cannot be determined, the foreign matter composition can be analyzed and compared with the material warehouse.DirtIt is necessary to distinguish whether it is caused by machine, man-made or the material itself.Bad bubbleIt is mainly divided into three forms:Open bubbles are caused by the matching of ink thickness with OCA and machine parameters.Nucleated bubbles: caused by foreign matters.Pure bubbles: air remains in the bonding layer to form real pure bubbles.DysfunctionPoor TP: poor open circuit, IC crush, ESD injury, etc.Poor module display: abnormal display, mura, black screen, etc.